1. Field of the Invention
The present invention relates to a new and distinct variety or cultivar of the ornamental tree, Acer saccharum, subspecies commonly known as Caddo sugar maple.
2. Description of the Related Art
Sugar maple trees are native over a huge range of North America and have been admired in particular for their fall foliage color beginning with the earliest settlers. Sugar maple trees have been planted in a variety of landscape situations for shade, form, wind shelters but particularly for fall foliage colors. In the general area east of the Mississippi river and north of about the 35th parallel the tree grows well in a range of environmental conditions. However, west and south of this area due to the relentless winds, low humidity and drought, plus the tendency of the soils to be more alkaline, the tree survives, but appearance is poor. Leaves of the eastern sugar maple tend to tatter and tear at the margins due to the winds and by mid to late summer leaves typically suffer from moderate to severe scorch and chlorosis of leaf margins, such that fall color is rendered poor to non existent.
During one or more of the North American periods referred to as an ice-age, tree species native to northern latitudes were forced to migrate south. When the ice receded and conditions became more hospitable, seedlings were dispersed from existing trees and over eons of time, migrated back to northern habitats. There are numerous examples of existing remnant plants of a northern species that have adapted and continue to survive in southern microclimates. One example is the remnant populations of American basswood, Tilia americana, trees found in unique microclimates of what is referred to as the hill country in west-central Texas. Another example is the population of sugar maple trees that remained and evolved in the canyons of west-central Oklahoma and the Texas panhandle area. The native habitat of these remnant trees is primarily in the accumulated debris near the base of steep canyon walls. These trees have developed thick leathery leaves and greater tolerance to drought and drying winds and alkaline soils compared to eastern sugar maple. When seedlings are moved from the protected canyon environment and planted in open windswept and more drought prone locations, the trees continue to resist the tough environmental assault.
Growing the tree from seed is difficult and impractical except on a very limited scale. Viable seeds are produced only every few years and from a given seed lot, germination may range from none to rarely more than 20%. Further, among the germinated seeds, only a fraction grow to make desirable trees and at a growth rate sufficient to be practical for commercial nurseries.
U.S. Plant Pat. No. 11,119 disclose a sugar maple tree with thick leathery glossy deep green leaves with good resistance to leaf tatter that is common to sugar maple trees. U.S. Plant Pat. No. 16,733 disclose a sugar maple tree having brilliant and unique fall color presentation and an upright structure that develops into a full spreading crown. U.S. Plant Pat. No. 19,807 disclose a sugar maple tree characterized by consistent vibrant orange fall colors in hardiness zone 8, heat tolerance and vigorous growth rate. In 2003, a sugar maple of Caddo origin with dark green summer foliage and brilliant, red early fall color was introduced under the cultivar name ‘John Pair’. However, this tree is substantially different in that it flowers and produces seeds and grows only about six to eight inches per year according to information released. Such slow growth reduces its acceptance by the nursery industry as well as anyone planting it in the landscape.
The new variety of sugar maple tree claimed herein, which has been given the cultivar name ‘WHIT XLV’ was selected from a block of Caddo sugar maple seedlings resulting from seed collected from a tree in Stillwater, Okla. in 1994. There are no records as to the source of the parent tree and the parent tree was destroyed during a storm in 1999. Interest in Caddo sugar maple trees is of long standing by plant enthusiasts. Beginning in 1973, seeds from Caddo sugar maple trees growing in their native habitat in southwest Oklahoma were collected and compared to seed collected from various trees in landscapes and parks around the state. Seedlings from the selected parent tree in Stillwater, Okla. consistently had greater vigor compared to seeds from other parents. Of the seeds collected in 1994, five seedlings stood out from the rest and were saved when all others were judged to be culls and destroyed. Among these five, one grew faster and was judged superior and in the 16 years of working with this tree, it has never failed to produce spectacular fall color and regardless of whether the fall was especially wet or extremely dry.
This new and distinct sugar maple variety has never flowered or produced seed even though there are other trees resulting from the same parent and other parents within range for pollination. Being sterile is an advantage relative to the litter of seeds as occurs from eastern sugar maple and assures that the tree will never become invasive or weedy in landscapes.
This new and distinct sugar maple has been asexually reproduced by rooting softwood or semi-hardwood cuttings during May 2005, 2006, 2007, 2008, 2009 and 2010 from the discovered tree and placed under intermittent mist in a greenhouse. However, rooting percentages are low, ranging from zero to 30% and resulting plants grow slowly. By contrast, when budded onto eastern sugar maple seedlings, resulting plants grow with acceptable vigor to be viable in the nursery industry and are consistent with characteristics of the parent tree. Based on research I conducted in central Oklahoma years ago, eastern sugar maple seedlings survive even under severe drought and exposure but by mid summer become ugly due to foliage damage. In one study leaf tatter and chlorosis developed on eastern sugar maple seedlings even when maintained throughout the growing season with adequate water. These studies suggest that the root system of eastern sugar maple is adapted to a much wider range than the foliage and that the leaf tatter and chlorosis often cited as a problem with eastern sugar maple is strictly a foliage phenomenon. Therefore, budding this new and distinct Caddo sugar maple cultivar ‘WHIT XLV’ onto eastern sugar maple seedlings provides a superior root system—top combination.